This invention relates generally to bottling machines and in particular it relates to a filling machine for charging containers, such as bottles and the like, with a liquid from an annular tank equipped with a filling system having a liquid discharging pipe, a gas returning conduit and a pressure control space surrounding the filling pipe and connectable through a pressure relief channel with the outer atmosphere.
In German Pat. No. DP-GBM 1.968.011 a filling system is described which includes a valve arranged in the gas return conduit opening into the gas pressure space of a rotary liquid tank and permitting a connection of the gas return conduit with the outer atmosphere. The control of this valve is effected by means of stationary stops or cam surfaces arranged in the path of movement of the tank and abutting against projecting push rods of the valve. The system has further a filling unit including a filling valve in the form of an elongated pipe and upon applying the filling unit against the container to be filled the pressure between the container and the tank is equalized. As soon as the equal pressure in the container is built up, the filling valve opens and the liquid flows into the bottles by the action of gravity. In addition, there is provided a device that makes it possible to create a pressure difference resulting in an increased speed of the liquid during its discharge to the bottle. In the normal course of filling operations the valve arranged in the gas return channel communicating with the liquid tank is opened and connects the gas return conduit to the outer atmosphere. Consequently a considerable pressure difference is created that effects a faster discharge of the liquid. The valve itself is controlled by means of outside control cams arranged at the circular track of the filling machine. If the filling machine for one reason or another decelerates its rotary motion, or if it stops and starts again, there is no possibility to control this valve so that the quick filling action continues until the whole filling process is terminated. This shortcoming, however, can make considerable operational difficulties since during the slowdown of the movement of the filling machine a considerable part of the liquid is discharged into widely branched channels in the filling unit and the spilled liquid can prevent an exact definition of the filling level that is essential in the filling operation. This failure occurs not only during a momentary interruption of the rotary movement of the filling machine but also during its coasting or restarting. In the endeavor to diminish this disturbance, the stationary control cams for each atmosphere valve has been made tiltable. In modern bottling machines having large diameters and circumferential speeds this tiltable arrangement is no longer applicable because due to correspondingly increased power the inertia effects of the system would prevent an exact control. For example, the auxiliary mechanical control of the cams is completely out of the question in filling machines controlled according to their output so that all cooperating devices are correlated according to the rate of the liquid discharge. Another disadvantage of the known devices resides in the fact that due to relatively narrow channels the liquid particles produce undefinable throttling or choking effects so that pressure differences vary and these pressure variations may cause again inaccurate filling of the bottles. These undesired effects may take place even in an arrangement where, in order to define the pressure difference, chokes or restrictions are provided in the return gas or return air conduits because bubbles especially in the case of CO.sub.2 containing liquids, and/or liquid remainders change the prearranged choking gap.